BELGRADE, Serbia (CNN) --U.S. Secretary of State Colin Powell said Wednesday he was "absolutely delighted" with Serbia's commitment to reforms started by the late Prime Minister Zoran Djindjic, assassinated last month.

Powell, who was making a brief visit to Belgrade, said during a joint news conference with new PM Zoran Zivkovic: "The aggressive action under way against criminals and others who would destroy your society is the greatest tribute you could pay."

"(Djindjic's) assassination has unleashed forces which will obliterate the evil situation that caused his death," Powell said. (Special report)

Serbia and Montenegro have been plagued by organized crime, war criminals and political extremism. In February, the two countries formed a loose federation and are working to resolve these problems.

"I come to demonstrate strong U.S. support for Serbia and Montenegro after the assassination of Prime Minister Zoran Djindjic, a friend of mine," Powell said. "I admired him greatly as a leader and as a friend."

Powell's visit to Belgrade is part of a trip to Europe. He visited Turkey earlier Wednesday and was due in Brussels for a meeting with NATO and European Union members Thursday.

He said he planned to visit Djindjic's widow to express his condolences before leaving Belgrade.

Powell struck a conciliatory tone during his visit to Ankara, where he said Turkey would play a "big role" in Iraq's postwar reconstruction. (Powell's assurance)

In a joint press meeting with Turkey's Foreign Minister Abdullah Gul, Powell said he was disappointed parliament had refused in March to let U.S. troops use Turkish territory to launch an invasion into northern Iraq. But he said the issue has not affected the war effort.

"As the result of flexible planning and a great deal of skill on the part of our commanders, we've been able to work around that, and we are now deeply appreciative of the overflight clearances that have been provided by the parliament and the Turkish government," Powell said.

"Tensions have lessened," he added.

He said Turkey would be able to provide Iraq with a good example of a Muslim democracy as Baghdad forms a government after the war.

Gul added: "Turkish-American relations are based on very strong foundations. Currently, we have a war in the region, which could not be prevented, unfortunately.